The use of an LMIS and argon ion sputtering in studies of thin film strain gauges

Abstract

The gauge factor of a material, is an important property which gives insight into certain electron scattering mechanisms occurring within a material; its size and reproducibility feature strongly in the selection of materials for use as commercial strain gauges. Gauge factor measurements have been made on gold films prepared using: (a) conventional vacuum evaporation and subsequent etching to various depths using a low energy argon ion beam; (b) vacuum evaporation and subsequent mechanical surface roughening; (c) a liquid metal ion source. Films prepared by these techniques exhibit differing values for the gauge factor. This arises from differences in the microstructure of the films produced by these methods. Comparisons are made between the measured gauge factors and the appropriate theoretical models. It is shown that previous comparisons between the measured gauge factors and theory are incorrect. These gauge factors had included the presence of non-strain sensitive terms in the total resistance arising from defects and impurities. In the present work residual resistance measurements were made, enabling such contributions to be identified.